"We went about this with the thought we were playing a game this weekend, and we had to make a choice of who would go out with the first group, which really tells us who is ahead at this time," USC head coach Pete Carroll said. "And, Aaron Corp is that guy."

Corp entered the spring with a slight lead and held off a surging Barkley by playing consistently and by taking care of the football. Corp hasn't thrown a single interception all spring.

"He's had a great spring, and he's done everything he can to maximize this opportunity at this point," Carroll said. "He understands the offense. He's moved around well with it.

"He's made his mistakes, but he's really been able to avoid the costly mistakes. That's what you like to see in your starting quarterback."

Corp received the news prior to Tuesday's practice.

"I'm excited," he said. "It's a great opportunity, but again, I can't get complacent. Matt's right there."

As the starter heading into summer, Corp will assume an expanded leadership role during offseason workouts and players-only practices.

Barkley's strong spring has earned him the No. 2 spot, and he'll lead the second-team offense during Saturday's scrimmage at the Coliseum.

"Matt's had an incredible spring," Carroll said. "He's just been off the charts and beyond our expectations of what a guy can do in his first semester, particularly coming out of high school early."

Carroll said Barkley wouldn't be able to play if USC had a game this weekend because he's behind on the offensive signals.

While the decision has been made now, the future is still up in the air. Carroll said as Barkley grasps more of the offense and as Mustain continues to battle, he expects the competition to resume at the start of fall camp.